The development of a high performance wideband radio frequency (RF) transceiver used in the next generation mobile communication system is presented. The developed RF transceiver operates in the 6 to 6.3 GHz band and the channel bandwidth is up to 100 MHz. It operates in the time division duplex (TDD) mode and supports the multiple-input multipleoutput (MIMO) technique for the international mobile telecommunications (IMT)-advanced systems. The classical superheterodyne scheme is employed to achieve optimal performance. Design issues of the essential components such as low noise amplifier, power amplifier and local oscillators are described in detail. Measurement results show that the maximum linear output power of the RF transceiver is above 23 dBm, and the gain and noise figure of the low noise amplifier is around 24 dB and below 1 dB, respectively. Furthermore, the error vector magnitude (EVM) measurement shows that the performance of the developed RF transceiver is well beyond the requirements of the long term evolution (LTE)-advanced system. With up to 8 x 8 MIMO configuration, the RF transceiver supports more than a 1 Gbit/s data rate in field tests.
A novel dual-band planar microstrip filter using parallel coupled microstrip lines and open-loop stepped-impedance resonators(SIRs)loaded with two shunt open stubs is presented.By tuning the physical lengths of open-loop SIRs,parallel coupled microstrip lines and two stubs,the bandpass filter has good dual-passband performance at 2.55 and 5.35 GHz and high isolation between the two passbands.The relative bandwidths of the two passbands are 11.8% and 16.8%,respectively.Compared with the conventional open-loop SIR filters,the designed filter has a comparatively broader fractional bandwidth at the second passband.So it can cover all the wireless LAN(local area network)bands.In addition,the filter has the features of low loss,high rejection and low ripple.The measured results are in good agreement with the simulated responses by HFSS software.
With the linear interpolation method, an improved absorbing boundary condition(ABC)is introduced and derived, which is suitable for the alternating-direction-implicit finite- difference time-domain (ADI-FDTD) method. The reflection of the ABC caused by both the truncated error and the phase velocity error is analyzed. Based on the phase velocity estimation and the nonuniform cell, two methods are studied and then adopted to improve the performance of the ABC. A calculation case of a rectangular waveguide which is a typical dispersive transmission line is carried out using the ADI-FDTD method with the improved ABC for evaluation. According to the calculated case, the comparison is given between the reflection coefficients of the ABC with and without the velocity estimation and also the comparison between the reflection coefficients of the ABC with and without the nonuniform processing. The reflection variation of the ABC under different time steps is also analyzed and the acceptable worsening will not obscure the improvement on the absorption. Numerical results obviously show that efficient improvement on the absorbing performance of the ABC is achieved based on these methods for the ADI-FDTD.